This invention provides aqueous dispersions of polystyrene and certain copolymers thereof formed in situ by polymerization of styrene and perhaps other selected monomers in the presence of selected water-dispersible sulfopolyesters. The resulting hybrid polyester/polystyrene dispersions are useful for simultaneously applying warp size and permanent coloration to filament yarns in preparation for weaving without including formaldehyde-releasing resins.
U.S. Pat. No. 5,912,281, assigned to Eastman Chemical Company, discloses similar aqueous dispersions useful in formulating rewettable printing inks. The styrene copolymers of U.S. Pat. No. 5,912,281 contain a minimum of about 7.5 weight % of a hydroxy(alkyl)methacrylate or hydroxy(alkyl)acrylate and a minimum of about 2 weight % of a carboxyl containing monomer. The aqueous dispersion proposed herein must contain ethylene terephthalate repeat units, whereas a broader range of sulfopolyesters and sulfopolyesteramides are said to be useful in U.S. Pat. No. 5,912,281.
It is known that a protective coating called a warp size may be applied to filament polyester yarns in preparation for weaving. Conventionally, this sizing is removed after weaving. Some years ago, it was discovered that a colorant could be applied to polyester yarns in the same operation that the warp size is applied, thus eliminating the need for a separate dyeing or pigmenting process. In this case, the sizing is not removed after weaving. This combined operation is often referred to as “slasher dyeing” or “slasher pigmenting.” It is particularly suitable for mattress ticking, drapery lining and other items that are not usually put into a washing machine. However, in order to obtain colorfastness on slasher-colored goods, i.e., to prevent bleeding or rub-off of the color in product use, it has been necessary to include formaldehyde in the sizing formula, along with a sulfopolyester, to secure the dye or pigment to the yarn. This practice has the unfortunate side effect of possibly releasing formaldehyde, a suspected human carcinogen, into the workplace atmosphere, into product showrooms and, ultimately, into the consumer's home.